1. Field of the Invention
The present invention relates to an ink jet recording head used in an ink jet recording apparatus such as ink jet printers or like recording apparatuses, and also relates to a method for manufacturing such an ink jet recording head, wherein, in operation, the ink jet recording head records an object, for example characters, images, patterns or like on a recording medium or sheet by ejecting ink droplets from an ink ejection nozzle of the ink jet recording head to realize a high quality gradation printing operation.
2. Description of the Related Art
Of various types of recording methods, a non-impact recording method is a favorable one since it is substantially free from any noise in recording operation. In recent years, the use of such the non-impact recording method in numerous applications has dramatically increased. Consequently, such non-impact recording method shows a wide variation in types. Of these types of the non-impact recording method, an ink jet recording method is advantageous in that: it is capable of directly recording any desired characters, images, patterns or like on a recording medium or sheet at a high recording speed through an ink jet recording apparatus with a simple construction in which the ink jet recording method is carried out; and, further, it is also capable of using ordinary paper as its recording medium or sheet, and therefore excellent in ease of use.
Heretofore, various types of the ink jet recording methods have been proposed, one of which is well known and carried out by the ink jet recording apparatus or printer. In such the ink jet recording apparatus or printer, ink droplets are ejected from an ink ejection nozzle of the ink jet recording head thereof to adhere to the recording medium such as paper, sheets or the like, so that the desired characters, images, patterns or the like are recorded on such recording media. This type of ink jet recording method is advantageous in that it is capable of: performing its recording operation at high speed; and, using ordinary paper as its recording medium without having such ordinary paper treated through a special fixing treatment in recording operation. Heretofore, numerous forms of ink jet recording apparatuses or printers for carrying out the above-mentioned ink jet recording methods have been proposed and commercially manufactured.
The ink jet recording methods are substantially classified into three major types: namely, a continuous ejection type; an on-demand type; and, an electrostatic absorption type. In the on-demand type ink jet recording method, a piezoelectric element of the ink jet recording apparatus for carrying out the on-demand type method is energized only at a predetermined moment or time when it is required, so that the ink droplets are ejected from the ink ejection nozzle of the ink jet recording apparatus at the above predetermined moment. As a result, the ink jet recording apparatus or printer for carrying out the on-demand type ink jet recording method is improved in ink consumption properties, and very simple in construction. Therefore, it is to be expected that such an on-demand type ink jet recording apparatus or printer will be widely used.
In this on-demand type of the ink jet recording apparatus, its conventional type ink jet recording head is constructed of: a pressure generating chamber which communicates with an ink reservoir; the ink ejection nozzle which communicates with the pressure generating chamber; a vibrating plate which forms a portion of the pressure generating chamber; and, the piezoelectric element which causes the vibrating plate to vibrate to intermittently increase a pressure in an interior of the pressure generating chamber to produce a pressure pulse therein, wherein such the pressure pulse forces ink of the pressure generating chamber to be ejected through the ink ejection nozzle outward and formed into the ink droplets.
In the conventional ink jet recording head through which the above-mentioned ink jet recording method is carried out, each of the pressure generating chamber, ink reservoir, ink ejection nozzle or like essential parts is formed by stacking a plurality of its components or plates into a pile. In this pile, each of the components or plates has been subjected to: an etching process performed from one surface of the component or plate to an other surface thereof; a stamping process performed by a machine punch or like press machines; an electroforming process; or, like processes, and thereby assuming a desired shape suitable for formation of above-mentioned individual essential parts of the conventional ink jet recording head.
FIG. 8 shows a cross-sectional view of an essential part of an example of the conventional ink jet recording head, illustrating the pressure generating chamber and the peripheral portions thereof. As is clear from FIG. 8, the conventional ink jet recording head is constructed of: a vibrating plate 60; a chamber plate 61 for forming the pressure generating chamber; and, an ink supply plate 62 for forming both an ink inlet passage 65 and an ink outlet passage 66, wherein these plates 60, 61 and 62 are stacked upon one another and firmly combined with each other to form the ink inlet passage 65, a pressure generating chamber 63, and the ink outlet passage 66; the ink inlet passage 65 receives the ink from the ink reservoir (not shown); the pressure generating chamber 63 is communicated with both the ink inlet passage 65 and the ink outlet passage 66; and, through the ink outlet passage 66, the ink is delivered to the ink ejection nozzle (not shown in FIG. 8).
In the conventional ink jet recording head having the above construction, a blank of the chamber plate 61 is subjected to the stamping operation performed by the machine punch. As a result, the above blank is provided with a through-hole defined by an inner edge surface 61a, and is therefore formed into the chamber plate 61. As viewed in FIG. 8, this inner edge surface 61a extends in a direction perpendicular to an upper or major surface of the chamber plate 61. The pressure generating chamber 63 is formed by closing both upper and lower openings of the above through-hole of the chamber plate 61 with the vibrating plate 60 and the ink supply plate 62, respectively. As for the ink inlet passage 65 and the ink outlet passage 66 both provided in the ink supply plate 62, each of these passages 65, 66 is formed through the stamping process performed by the machine punch, and thereby having its inner edge surface extending in a direction perpendicular to an upper or major surface of the ink supply plate 62, as is in the case of the above through-hole of the chamber plate 61.
Consequently, in operation of the conventional ink jet recording head having the above construction, the ink is supplied from the ink reservoir (not shown) through the ink inlet passage 65, pressure generating chamber 63 and the ink outlet passage 66, and has its flow path bent at substantially right angles on the midway to reach the ink ejection nozzle (not shown in FIG. 8).
Due to this, in the conventional ink jet recording head, there is a problem that some stagnation in the ink flow, formation of vapor bubbles, cavitation (which is caused by a large and sudden change in cross-sectional area of the ink flow passage), or like problems occur at corner portions 63a, 63b of the pressure generating chamber 63 and also in the vicinities of these corner portions 63a, 63b, wherein the corner portions 63a, 63b of the pressure generating chamber 63 directly receive the ink flow issued from the ink inlet passage 65 to have the ink flow bent at substantially right angles of its flow path. In case that the vapor bubbles and cavitation are produced in the ink flow at the corner portions 63a, 63b of the pressure generating chamber 63 in the conventional ink jet recording head, the piezoelectric element fails to build up a necessary pressure in the pressure generating chamber 63, because any pressure built up in the chamber 63 by energizing the piezoelectric element is absorbed by these vapor bubbles and cavitation. Consequently, in this case, the conventional ink jet recording head fails to have its ink properly ejected outward from its ink ejection nozzle, which makes it impossible to realize a high quality gradation expression of the ink droplets in recording operations.
In order to solve the above problems, it is necessary for the conventional ink jet recording head to have the through-hole of its chamber plate 61 (shown in FIG. 8) precisely positioned and stacked with the other components or plates in order to precisely form the ink passages together with the through-hole. Due to this, in the conventional ink jet recording head, it is necessary to have its components formed and assembled as precisely as possible. In other words, alignment in stacking of these components must be kept at the highest possible level.